1. Technical Field
The present invention is directed to an apparatus for measuring heat flow and methods related to the fabrication and calibration of such apparatus.
2. Description of Related Art
One of the major difficulties in developing novel thin film thermoelectric materials lies in obtaining consistent and accurate measurement of their thermal and electrical properties. Traditional methods cannot be easily extended to microscopic characterization because of increased electrical and thermal parasitic losses associated with the probes used to perform the measurements. Additionally, the poor structural stability of some of the novel materials being investigated makes using traditional probe methods unworkable.
For example, in the case of measurements using a probe, such as the xe2x80x9cZT-meter,xe2x80x9d the time-scales of the transients become short and introduce errors in the electrical measurements. Scanning thermoelectric microscopy (STEM) based on atomic force microscope (AFM) probes are capable of performing measurements of thermal and electrical properties of thermoelectric materials at these small scales. However, STEM based on AFM probes still have several limitations. For example, present probes only give qualitative measurements of heat flow, which only allows one to determine whether there is more or less heat flow with one material versus another. Therefore, it would be desirable to have a scanning heat flow probe that allows quantitative measurements of heat flow to be made.
The present invention provides a scanning heat flow probe for making quantitative measurements of heat flow through a device under test. In one embodiment the scanning heat flow probe includes an electric current conductor in a cantilever beam connected to a probe tip and coupled to two voltmeter leads. The probe also includes two thermocouple junctions in the cantilever beam electrically isolated from the electric current conductor and the two voltmeter leads. Heat flow is derived quantitatively using only voltage and current measurements. In other forms, the invention relates to the calibration of scanning heat flow probes through a method involving interconnected probes, and relates to the minimization of heat flow measurement uncertainty by probe structure design practices.